Up to now, quantitation of airborne antigen has relied on counting pollens and mold spores identifiable morphologically under the microscope or by their characteristics in culture. Availability of quantitative immunochemical sampling techniques now allows measurement of any particulate antigen providing reference standards exist and serum pools contain IgE antibody can be assembled. Our method uses an Accu-Vol sampler to collect airborne dust particles 0.3 microns and larger or a similar apparatus designed for quiet indoor use. Antigens are eluted from the fiberglass filter sheet and assayed by RAST inhibition. In Rochester, MN, we will measure Alternaria (and Alt-1) daily from April 1st to November 1st, 1984 or 1985 and determine the size of the allergen containing particles on three days each month using an Anderson sampling head. We will also assay for rye grass group 1, birch and oak pollens. The samples will be assayed also for airborne amorphous insect antigens. Indoors we will assay five homes weekly throughout the year for cat and house dust mite antigens. In collaboration with investigators in New Orleans and Tucson, we will assay ragweed, Alternaria, rye grass 1 and Bermuda grass and compare the seasonal levels at different sites. In collaboration with investigators in New York and San Francisco, we will measure levels of mite and cockroach antigens indoors and determine climatic and seasonal variations in indoor or concentrations of these antigens.